-=> On 09-29-97  08:19, Roy Witt said to Ivy Iverson,<=-
-=>"About High Gain Antennas for 2M...,"<=-
-=> 26 Sep 97 00:22, Ivy Iverson wrote to Roy Witt:
 
 RW> Hello Ivy.
 
HI, Roy;
 
 RW>> Some very interesting FB ratios...
 
 RW>>     o
 RW>>   /          top view
 RW>>  o------o-------o-------o-------o------o
 RW>>   \    DE
 RW>>     o
 II>
 II> Ah yes, the good old corner reflector... Now if you were to replace
 II> the dipole elements with a 5/8 J-pole and suitably-sized elements,
 II> mount them vertically on a boom, (about 6-8 Ft long?), I wonder what
 II> ERP you would get with about 40 Watts at the antenna, (50W xmtr)? ...
 
 RW> Build it correctly.  Mount it behind the reflector...This is about a
 RW> 7.5dbd  antenna with a much better F/B ratio than you'll find in a
 RW> normal Yagi.
 
I'm sure!  Are you talking 1/4 wave elements?  If it's built with 6 dB
J-poles, what would the gain be?  How about adding more 5/8 elements to
the J-poles?  Hey, might as well dream big, right?
 
And if you have a 6-8 Ft boom, that would be quite a strain to mount it
from behind.  I think it would be more effective to mount it at the center
of balance, on top of the supporting mast.  Do you REALLY want a 2M
"cannon"?  Have the J-poles paired, above AND below the mast!  Also, what
difference would it make if the corner had a screen instead of duned
reflectors?  This would require a non-metallic mast unless it were rear-
mounted, but if the DE's were properly phased and everything optimized
(resistors in the directors, etc?)...  That just MIGHT be hot enough for
moonbounce if it were mounted on AZ-EL rotors!  (It would also be about
15 Ft high and quite heavy with a lot of wind resistance!)
 
73 DE KB9QPM
   Ivy
 
 
 
... Double your dipoles. Double your flux.
 
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